Replace your boring wingnut with this vintage AERMOTOR CO. gauge that has been tapped to 1/4-20 threads to match a standard air filter threaded post. The indicator is 2.18" in diameter and 1.05 inches thick. The overall height is 3.16", so you'll need at least 3 1/4 inches of clearance under your hood — if you even have a hood on your ride.
